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101.
K.C. Kumara Swamy G. Gangadhararao R. Rama Suresh N.N. Bhuvan Kumar Manab Chakravarty 《Journal of organometallic chemistry》2010,695(7):1042-382
Phosphine-activated reactions of alkynes/alkenes/allenes as well as the Mitsunobu reaction involve a rich phosphorus chemistry. With the aid of simple cyclodiphosphazanes, characterization of many compounds analogous to the proposed intermediates in such reactions has been accomplished. Use of a cyclodiphosphazane in Pd-catalyzed N-arylation reactions is highlighted. Results on molecular non-stoichiometry in phosphorus compounds and on the use of chiral phosphorus systems are discussed. Synthesis of allenylphosphoramides involving a cyclodiphosphazane is also described. X-ray structures of the new compounds [(t-BuNH)(PhCH2CH(CN)CH2-)P(μ-N-t-Bu)2P(NH-t-Bu)]+[HCO3]− (13), [(t-BuNH)P(μ-N-t-Bu)2P(N-t-Bu)-C(CH2)CH(C6H4-4-Me)-P(O)(OCH2CMe2CH2O)] (18), [(i-PrNH)P(μ-N-t-Bu)2P(N-i-Pr)-N(CO2-i-Pr)-NH(CO2-i-Pr)] (24), [(S)-(2-OH-1-C10H6-1′-C10H6-2′-O-P(O)(NH-t-Bu)2] (36) and [(t-BuNH)(O)P(μ-N-t-Bu)2P(O)(CHCCMe2)] (40) are also reported. 相似文献
102.
Aldehydes and ketones undergo a smooth reductive etherification by polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding symmetrical ethers in excellent yields. This new reagent system (PMHS/I2) provides a simple and convenient route for the preparation of symmetrical ethers from carbonyl compounds. 相似文献
103.
104.
An overview of sample preparation and extraction of synthetic pyrethroids from water,sediment and soil 总被引:1,自引:0,他引:1
Saeed S. Albaseer R. Nageswara Rao Y.V. Swamy K. Mukkanti 《Journal of chromatography. A》2010,1217(35):5537-5554
The latest developments in sample preparation and extraction of synthetic pyrethroids from environmental matrices viz., water, sediment and soil were reviewed. Though the synthetic pyrethroids were launched in 1970s, to the best of authors’ knowledge there was no review on this subject until date. The present status and recent advances made during the last 10 years in sample preparation including conservation and extraction techniques used in determination of synthetic pyrethroids in water, sediment and soil were discussed. Pre- and post-extraction treatments, sample stability during extraction and its influence upon the whole process of analytical determination were covered. Relative merits and demerits including the green aspects of extraction were evaluated. The current trends and future prospects were also addressed. 相似文献
105.
106.
U. M. Swamy G. C. Rao R. V. G. Ravi Kumar Ch. Pragati 《Southeast Asian Bulletin of Mathematics》2003,26(3):509-516
In this paper, it is proved that the Boolean centre of a semigroup S with sufficiently many commuting idempotents is isomorphic to the inverse limit of the directed family of Birkhoff centres (or Boolean centres) of a class of bounded semigroups. The Birkhoff centre is defined for any poset and proved that it is a relatively complemented distributive lattice whenever it is nonempty. It is observed that for a semilattice S, the Birkhoff centres as a semigroup and as a poset coincide. Also it is observed that for a Lattice (L, , ), the Birkhoff centres of the semilattices (L, ) and (L, ) coincide with the Birkhoff centre of L. Finally it is proved that for a lattice (L, , ), the Boolean centres of the semilattices (L, ) and (L, ) coincide with the Boolean centre of L.AMS Subject classification (1991): 06A12, 20M15 相似文献
107.
Steady-state and time-resolved fluorescence spectroscopic studies have been carried out on Trichosanthes cucumerina seed lectin (TCSL). The fluorescence emission maximum of TCSL in the native state as well as in the presence of 0.1 M lactose is centered around 331 nm, which shifts to 347 nm upon denaturation with 8 M urea, indicating that all the tryptophan residues of this protein in the native state are in a predominantly hydrophobic environment. The exposure and accessibility of the tryptophan residues of TCSL and the effect of ligand binding on them were probed by quenching studies employing two neutral quenchers (acrylamide and succinimide), an anionic quencher (I(-)) and a cationic quencher (Cs(+)). Quenching was highest with acrylamide and succinimide with the latter, which is bulkier, yielding slightly lower quenching values, whereas the extent of quenching obtained with the ionic quenchers, I(-) and Cs(+) was significantly lower. The presence of 0.1 M lactose led to a slight increase in the quenching with acrylamide and iodide, whereas quenching with succinimide and cesium ion was not significantly affected. When TCSL was denatured with 8 M urea, both acrylamide and succinimide yielded upward-curving Stern-Volmer plots, indicating that the quenching mechanism involves both dynamic and static components. Quenching data obtained with I(-) and Cs(+) on the urea-denatured protein suggest that charged residues could be present in close proximity to some of the Trp residues. The Stern-Volmer plots with Cs(+) yielded biphasic quenching profiles, indicating that the Trp residues in TCSL fall into at least two groups that differ considerably in their accessibility and/or environment. In time-resolved fluorescence experiments, the decay curves could be best fit to biexponential patterns, with lifetimes of 1.78 and 4.75 ns for the native protein and 2.15 and 5.14 ns in the presence of 0.1 M lactose. 相似文献
108.
M. S. R. Swamy T. P. Prasad B. R. Sant 《Journal of Thermal Analysis and Calorimetry》1979,16(2):471-478
The thermal decomposition of ferrous sulphate heptahydrate was carried out in air under dynamic and isothermal conditions. The intermediate phases were identified by chemical analysis and an X-ray technique. Ferrous sulphate heptahydrate is converted to tetrahydrate and monohydrate, but this conversion is accompanied by oxidation. Fe(OH)SO4 and Fe2O(SO4)2 are formed as oxidation products, and the latter decomposes to ferric oxide directly and/or through Fe2(SO4)3.
The authors express their grateful thanks to Prof. P. K. Jena, Director, for his keen interest and permission to publish the paper, and to Dr. A. Lakshminarayana for the X-ray measurements. One of us (MSRS) also thanks the Regional Research Laboratory (CSIR) for a fellowship. 相似文献
Zusammenfassung Die thermische Zersetzung von Eisen(II)sulfat Heptahydrat wurde in Luft unter dynamischen und isothermen Bedingungen durchgeführt. Die Intermediärphasen wurden durch chemische Analyse und Röntgentechnik identifiziert. Eisen(II)sulfat Heptahydrat wird in Tetrahydrat und Monohydrat überführt, doch wird diese Umwandlung durch eine Oxidation begleitet. Fe(OH)SO4 und Fe2O(SO4)2 werden als Oxidationsprodukte gebildet und letzteres wird unmittelbar und/oder über Fe2(SO4)3 zu Eisen(III)oxid zersetzt.
Résumé La décomposition thermique dans l'air du sulfate de fer(II) heptahydraté a été étudiée en conditions dynamiques et isothermes. Les phases intermédiaires ont été identifiées par analyse chimique et par rayons X. Le sulfate de fer(II) heptahydraté se transforme en tétrahydrate et en monohydrate mais cette conversion s'accompagne d'une oxydation. Il se forme Fe(OH)SO4 et Fe2O(SO4)2 comme produits d'oxydation et ce dernier se décompose en oxyde de fer(III) directement ou quelquefois avec formation intermédiaire de Fe2(SO4)3.
(II) . . (II) . Fe(OH)SO4 Fe2O(SO4)2. (III) Fe2(SO4)3.
The authors express their grateful thanks to Prof. P. K. Jena, Director, for his keen interest and permission to publish the paper, and to Dr. A. Lakshminarayana for the X-ray measurements. One of us (MSRS) also thanks the Regional Research Laboratory (CSIR) for a fellowship. 相似文献
109.
Satish Kumar N Kommana P Vittal JJ Kumara Swamy KC 《The Journal of organic chemistry》2002,67(19):6653-6658
Diisopropyl azodicarboxylate (DIAD) undergoes a cycloaddition reaction with the cyclic phosphites CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)PX (1) [X = NCS (a), N(3) (b), Cl (c), NHMe (d) and Ph (e)] to afford the novel pentacoordinate phosphoranes 2a-e as crystalline solids. This result is different from the reaction of PPh(3) with DIAD used in the well-known Mitsunobu reaction. X-ray crystallography of 2a, 2b, and 2d reveals that the nitrogen, rather than the oxygen, occupies an apical position of the trigonal bipyramidal phosphorus. This is in violation of the commonly accepted preferences for substituents in trigonal bipyramidal phosphorus. In 2e, although the oxygen of the five-membered ring occupies the expected apical position, the phenyl group also occupies (the other) apical position, forcing the more electronegative oxygen atoms of the eight-membered ring to span equatorial-equatorial positions. In contrast to the above, the isocyanato compound CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)PNCO (1f), upon treatment with DIAD, affords compound 3 to which a tetracoordinate structure is assigned. 相似文献
110.
Reaction of the cyclodiphosphazane [(OC4H8N)P(μ‐N‐t‐Bu)2P(HN‐t‐Bu)] ( 1 ) with an equimolar quantity of diisopropyl azodicarboxylate afforded the phosphinimine product [(OC4H8N)P(μ‐N‐t‐Bu)2P=N‐t‐Bu)(N(CO2 ‐i‐Pr)NHCO2‐i‐Pr] ( 6 ) having a PIII‐N‐PV skeleton. Similar products [(t‐BuNH)P(μ‐N‐t‐Bu)2P=N‐t‐Bu)(N(CO2Et)NHCO2Et] ( 7 ) and [(CO2‐i‐Pr)HNN(CO2‐i‐Pr)](t‐BuN=P(μ‐N‐t‐Bu)2POCH2CMe2CH2O[P(μ‐N‐t‐Bu)2P=N‐t‐Bu)(N(CO2‐i‐Pr)NH(CO2‐i‐Pr)] ( 8 ) were spectroscopically characterized in the reaction of [(t‐BuNH)P‐N‐t‐Bu]2 ( 2 ) and [(t‐BuNH)P(μ‐N‐t‐Bu)2POCH2CMe2CH2OP(μ‐N‐t‐Bu)2P(NH‐t‐Bu)] ( 3 ) with diethyl‐ and diisopropyl azodicarboxylate, respectively. By contrast, the reaction of [(μ‐t‐BuN)P]2[O‐6‐t‐Bu‐4‐Me‐C6H2]2CH2 ( 4 ) and [(C5H10N)P‐μ‐N‐t‐Bu]2 ( 5 ) with diisopropyl azodicarboxylate afforded the mono‐ and bis‐oxidized compounds [(O)P(μ‐N‐t‐Bu)2P][O‐6‐t‐Bu‐4‐Me‐C6H2]2CH2 ( 9 ) and [(C5H10N)(O)P‐μ‐N‐t‐Bu]2 ( 10 ), respectively. Oxidative addition of o‐chloranil to 7 and its DIAD analogue [(t‐BuNH)P(μ‐N‐t‐Bu)2P=N‐t‐Bu)(N(CO2‐i‐Pr)NHCO2‐i‐Pr] ( 11 ) afforded [(C6Cl4‐1, 2‐O2)(t‐BuNH)P(μ‐N‐t‐Bu)2P=N‐t‐Bu)(N(CO2R)NHCO2R] [R = Et ( 12 ) and i‐Pr ( 13 )] containing tetra‐ and pentacoordinate PV atoms in the cyclodiphosphazane ring. The structures of 6 , 9 , 12 and 13 have been confirmed by X‐ray structure determination. For comparison, the X‐ray structure of the double cycloaddition product [(C6Cl4‐1, 2‐O2)(t‐BuNH)PN‐t‐Bu]2 ( 14 ), obtained from the reaction of 2 with two mole equivalents of o‐chloranil is also reported. 相似文献